In the prior art, an image reading apparatus to be mounted on a copier, a scanner, or a multifunction device having the functions of the former is known to have an automatic document feeder (ADF) for transferring a document from a input tray through a transfer path to an output tray (for example, see JP-A-10-87108). There is also known an automatic document feeder by reversing leading and trailing ends of a document by reversible roller while the document is being transferred.
FIG. 15 shows a route in the automatic document feeder of the prior art. As shown, a document P placed on an input tray 100 with its first side (or first page) is being directed upward is fed by a pick-up roller 101 to a transferring path 102 by a pick-up roller 101. In the transfer path 102, the document P is transferred by suitably disposed transfer rollers 103 so that its first side is scanned while passing through a scanning position X by image reader such as a charge-coupled device (CCD) or a contact image sensor (CIS). When the document P having its first side read is detected at its trailing end by a sensor, reversible rollers 104 are stopped while nipping the trailing end of the document.
As shown in FIG. 16, the reversible rollers 104 reverse the transfer direction of the nipped document to a return path 105. The document P transfers again from the return path 105 to the upstream side of the scanning position X of the transfer path 102. As a result, the leading end and the trailing end of the document P are reversed. Then, the document P is transferred by the transfer rollers 103 so that its second side is read while being passed through the scanning position X by the image reader. When the document P having its two sides scanned is detected at its trailing end by the sensor, the reversible rollers 104 are stopped again while nipping the trailing end of the document. The document P having transferred again from the return path 105 into the transfer path 102 is reversed again at its leading end and the trailing end entering a state in which the first side opposes the scanning position X. Then, the document P is transferred through the transfer path 102 and then is discharged with its first side being in a downward direction relative to an output tray 106. As a result, the document P has both its sides read, and is discharged to the output tray 106 in the same order as when the document was placed on the input tray 100.